The present invention relates to an apparatus and method for a chemical-mechanical polishing (CMP) system, and more particularly, to an apparatus and method for conditioning the polishing pad of CMP system.
The chemical-mechanical polishing (CMP) is a new technology in integrated circuits (IC) manufacturing industry. During a process of IC manufacturing, a planarization process is often applied to perform on the surface of a semiconductor wafer. Of the different processes of planarization, CMP is the most effective one in xe2x80x9cglobal planarizationxe2x80x9d technology, that is, it can provide a fully planar surface of semiconductor wafers. And chemical-mechanical polishing is one of the most widely used processes for planarization before performing a multilevel metallization process.
Typically, a basic configuration of a CMP apparatus includes a polishing platen for holding a polishing pad, a wafer holder for holding a semiconductor wafer. Generally, the polishing pad has an abrasive top surface that contacts the semiconductor wafer. Besides, a vacuum chuck (not shown) set in the wafer holder applies negative pressure to the backside of the semiconductor wafer, thereby securely holding the wafer. For the xe2x80x9cchemical partxe2x80x9d, some slurry with specific chemical solutions is continuing to add onto the polishing platen during a CMP process. Usually, the chemical solution is mainly a compound of colloidal silica (or dispersed alumina) mixed with the solutions of potassium hydroxide (KOH) or ammonia (NH4OH). The abrasive materials in the slurry interact with the surface of a wafer in order to remove the unwanted surface layers of the wafer. For the xe2x80x9cmechanical partxe2x80x9d, the material of surface layers of a wafer is removed by the polishing pad. In operation, the wafer holder applies the top surface of the wafer against the abrasive top surface of the polishing pad. And the wafer holder is then rotating at a predetermined speed to polish the wafer against the polishing pad.
A CMP system further includes a conditioner (dresser), which is used to polish and recondition the polishing pad during a polishing process. The conditioning operation is one of the key process parameters. Referring to FIG. 1, it is a cross-sectional view diagram of a prior art polishing apparatus and polishing pad conditioner for CMP system. The wafer holder 100 is used to hold a semiconductor wafer 102. And the wafer holder 100 exerts force on the top surface of the wafer against the abrasive top surface of the polishing pad 104 on a platen 106. The polishing pad 104 is then driven by a drive motor 108 and is rotating at a predetermined speed in order to remove the unwanted material on different layers of the semiconductor wafer 102 thereon. A polishing pad conditioner 110 is applied to polish and recondition the polishing pad 104 during a CMP process. The polishing pad conditioner 110 has a holder 112 and an abrasive grinding layer 114, and the holder 112 is driven to rotate by a drive motor 116. And a top view of the configuration of the conventional polishing apparatus and polishing pad conditioner for CMP system is shown in FIG. 2, wherein the wafer holder 200 and the conventional polishing pad conditioner 202 are over a polishing pad 204.
The main function of applying a conditioner for CMP system is to restore the removal rate performance of the polishing pad; otherwise, the efficiency of the CMP decreases and the throughput of the wafer polishing declines as the CMP process is in proceeding. Because the removal rate of CMP is highly correlated to the conditioning quality of the polishing pad, the functions and performance of a conditioner is demanding. The polishing rate, or the removal rate, of a conventional CMP system will be unstable and not easy to control the removal amount by the pad profile exactly. To make matters worse, the pre-CMP deposition thickness is usually not uniform from the center to the edge. Thus, the peripheral and central portions of the polishing pad will not be removed by the conditioner in order to get a desirable profile. If the pad conditioning (dressing) is not enough or not uniform during CMP process, the polishing rate will be too low and become unstable, and the non-uniformity within a wafer will be even worse. Additionally, in prior art, a conditioner dresses a polishing pad throughout the surface of the pad. In this case, the conditioner can hardly be controlled to generate a specific profile of the pad.
An apparatus and method for conditioning the polishing pad of CMP system by employing a multi-zone conditioner, or dresser, is disclosed. The conditioner comprises a plurality of rollers or disks, and driving means for rotating the polishing rollers or disks.
The method of conditioning (dressing) is to condition the polishing pad in a multi-zone style. The conditioner comprises a plurality of rollers or disks, which can be well tuned to make down-pressure and rolling speed of the rollers or disks to the extent as desirable. The conditioner further comprises driving means for rotating the polishing rollers or disks. It can make a better uniformity of the pad conditioning and improve the profile of the polished wafers. The apparatus and method for conditioning the polishing pad can be especially used to compensate the uniformity of the incoming films, or the pre-CMP films.
The present invention provides an apparatus and method to improve the conditioning rate and the surface quality of the polishing pad. It provides a stable polishing rate and good non-uniformity within a wafer. Moreover, any desirable profile of polishing pads used to compensate incoming film profiles can be easily obtained by applying the apparatus and method of the present invention. Additionally, a plurality of conditioning units is integrated to one set of the conditioner, and each unit is a roller (or disk) type. The rolling speed and down-pressure of each roller can be adjusted to meet the requirement of the desirable shape on each zone of the polishing pad to obtain the profile as needed. In order to smooth the sharp edge of the portion been conditioning; that is, to get a better uniformity of a polishing pad, the conditioner of the present invention is made to swing horizontally at a small angle. A megasonic or ultrasonic jet can be applied to further improve the pad defects.